The Cleveland-based greeting card company's shares jumped 15 percent on the news.
American Greetings, whose brands also include Carlton Cards, Recycled Paper Greetings and Papyrus, said its board received the proposal from Chief Executive Zev Weiss and his brother, President and Chief Operating Officer Jeffrey Weiss, on Tuesday.
The group, which also includes other investors and members of the executives' families, wants to acquire all of the company's common stock that it doesn't currently own for $17.18 per share. That is a 20 percent premium over American Greetings' Tuesday closing stock price.
Based on the company's about 33.8 million outstanding shares, the offer values American Greetings at $580.7 million.
American Greetings said it expects its board to form a special committee of independent directors to consider the proposal. The company said it doesn't expect to make any further comments about the offer until a deal is struck or it rejects the bid.
American Greetings was founded over 100 years ago and went public in the 1950s. Members of the Weiss family currently make up a large part of its senior management. In addition to the brothers, their father, Mory Weiss, serves as the company's chairman, and Erwin Weiss, their uncle, is its senior vice president for specialty business.
In their letter to the company's board, the Weiss brothers said taking the company private will allow it to "return to its roots." While they have not secured financing, they said that they're confident they will be able to.
In June, American Greetings said its fiscal first-quarter profit dropped 78 percent, dragged down by charges related to the bankruptcy of Britain's Clinton Cards PLC. Total revenue fell 3 percent to $393.1 million. The company is scheduled to release second-quarter results Friday.
American Greetings had acquired about 400 Clinton Card stores earlier in June, along with the namesake brand.
The U.K. greeting card company is one of American Greeting's biggest customers, but ran into financial trouble. It had about 750 stores before being placed under administration last month.
In heavy morning trading, shares of American Greetings rose 15 percent, or $2.14, to $16.48, after peaking at $17.10 earlier in the day. The stock is down about 24 percent from its 52-week high of $21.68, reached a year ago.